Preface: why this book?
‘Quantum computing will change everything,’ the man in front of me said. Standing tall and confident, he took another sip of his drink before continuing, ‘It will be the biggest revolution since the invention of the transistor. Imagine a world where we can cure any disease with personalised medicine. A world where new energy sources will free us from our dependence on fossil fuels. Not to mention that…’
‘Well—’ I tried to interrupt, but the man passionately rattled on.
‘It will finally enable us to build general Artificial Intelligence that can take over our tedious everyday jobs, so 95% of our population no longer has to work!’
‘You know that quantum computers are still quite some years away, right?’, I countered. He leaned in, eyes still gleaming with excitement.
‘That’s what most people think. But the reality is, we’re closer than ever. Quantum supremacy has already been achieved. Google did it in 2019. Since then, progress has been exponential. Did you see the presentation by that guy from Goldman Sachs? Their investments already see higher returns than ever since their new Monte Carlo algorithm.’
The above conversation captures a feeling that many seasoned experts in quantum computing will have. A group of enthusiasts presents ‘quantum’ as a revolutionary technology with unprecedented capabilities. Plentiful reputable sources report how next-generation devices are key in tackling climate change, revolutionising AI, and building unhackable networks.
Experts who are actually building quantum computers are much, much more reluctant. At an academic conference, you hear a completely different story. Scientists ridicule the absurd claims that some consultants and startups make. They will point out that the applications of quantum computers are still very much uncertain and that we’re still searching for convincing use cases.
The quantum scene seems divided into two distinct worlds. One is the business world, eager to reach out to anybody who will hear them about the game-changing capabilities of quantum computers. The other is a more cautious community of scientists and technical experts who quietly bring quantum computers to reality, sharing their results in specialised papers that require a PhD to understand.
I was fascinated by this paradoxical situation. Who is right? How powerful are these quantum computers really, and how do they compare to existing technologies? In what year will we have a large-scale quantum computer, and what will it look like? These are billion-dollar questions, but the answers will vary wildly, depending on who you ask.
After searching for these answers for a decade, I’ve finally found a unique position to answer most of these questions. As a former academic researcher, I acquired a detailed understanding of quantum computers and their algorithms. For the past four years, I have had the privilege of forming R&D collaborations with startups, enterprises and governments while having countless meetings with CEOs, research leads and policymakers. I’ve seen the perspectives from both worlds and can cut through dishonest and deceptive claims. Additionally, after training many new colleagues and setting up professional learning programs, I developed a good intuition about what newcomers want to know about quantum technology and how to explain it in an accessible way.
However, the decisive factor that led me to write this book is my discomfort with other sources. Like many others in this field, I’m unhappy with the many hyped and unbalanced articles that would otherwise populate the top entries in Google search results (or even the New York Times best-selling books1). There is a clear need for a neutral source of information that others can reference when disagreeing about facts or debunking myths, and I’m very happy that it’s finally complete.
That doesn’t mean that this book contains only confirmed facts – not at all! Writing about a computer of the future comes with mountains of uncertainty. In 2005, nobody could have predicted that a mere five years ahead, everyone would be playing games and consuming the internet on their smartphones. In 2015, nobody could have predicted the impact of Large Language Models like ChatGPT. And indeed, today’s best predictions of a future quantum revolution won’t be quite so accurate either.
Even worse, experts wildly disagree in several cases. For example, the usefulness of quantum AI and optimisation is vigorously disputed, and the rate at which hardware will progress depends on many yet-to-discover breakthroughs. The best I could do is describe various perspectives on these matters and highlight the best arguments from both sides.
My colleagues and I had many discussions and disagreements, without which I wouldn’t have been able to gather the facts and opinions in this book. And it shouldn’t stop there. I keep welcoming criticism, opinions, and feedback about these complex topics, aiming to refine these texts even more in future updates.
Even though much is still uncertain, I think that a reliable indication of the prospects of quantum computing is more important than ever. Quantum startups are acquiring huge investments, allowing them to hire managers, software developers, salesmen, and marketers. Governments need informed policymakers, and journalists should cover quantum breakthroughs. Pretty much every organisation that deals with IT will want to keep a close eye on the impact that ‘quantum’ will have on them.
This book is for precisely these people who don’t need to understand all the technical details but still need to talk, read, and write about quantum technologies. We won’t care so much about the underlying math or physics but rather about the functionality of a quantum computer: the opportunities, the threats, and the concrete actions organisations can take.
How should you read this book? I chose to split the content into three parts. The first part contains the essentials that we recommend for everyone to read. This is an incredibly efficient way to learn all the background that you need – you should be ready to understand other sources and have some depth in professional discussions or meetings. To go into more detail, parts two and three contain more information about the (software) applications and the (hardware) devices, respectively. A final fourth part is reserved for additional resources that can be useful or fun when continuing your quantum journey.
I’m referring to Michio Kaku’s book ‘Quantum Supremacy’, but before you even consider reading it, you might like to see the book review by a professor in quantum computer science (https://scottaaronson.blog/?p=7321). ↩